ISSN (Online) : 2278-1021 ISSN (Print) : 2319-5940 International Journal of Advanced Research in Computer and Communication Engineering Vol. 3, Issue 1, January 2014

Bluetooth Hotspot

Pooja Abnave1, Priyanka Patil2, P.L.Himabindu3, Prashant Dukare4, S.S.Vanjire5 Student, Department Of Computer Engineering, University of Pune, Pune, India1 Student, Department Of Computer Engineering, University of Pune, Pune, India2 Student, Department Of Computer Engineering, University of Pune, Pune, India3 Student, Department Of Computer Engineering, University of Pune, Pune, India4 Assistant Professor, Department Of Computer Engineering, University of Pune, Pune, India5

Abstract: Bluetooth is a technology for short range wireless real-time data transfer between devices. It is becoming increasingly more prevalent in modern society, with technical gadgets now ranging from mobile phones and game controllers to PDAs and personal computers. Bluetooth hotspot is a technology which allows Bluetooth enabled mobiles (clients) to access the internet. With this technology mobile phones need not have a GPRS connection in it. Before accessing the internet Bluetooth mobiles (devices) need to be discoverable. The Bluetooth server discovers all devices in its range and sends a message for pairing. The connection link is established when an appropriate message is sent by the discovered device for pairing in response to the servers message. In this paper we will study how communication links are established, what are the security issues and how they are handled in Bluetooth and the data packet format.

Keywords: Eavesdropping; Ad-hoc network; Bluetooth Network; Bluetooth Security; Media Access

I. INTRODUCTION II. NEED Ad hoc networks today are based primarily on Bluetooth As the number of Bluetooth products increases each year, it technology. Bluetooth is an open standard for short-range is important to develop applications and services to take full digital radio. It is touted as a low-cost, low-power, and low advantage of their potential and capabilities. A broadband profile technology that provide a mechanism for creating hotspot is one application where Bluetooth has a value in small wireless networks on an ad hoc basis. Bluetooth is providing Internet access to mobile users. Consumers considered a wireless PAN technology that offers fast and owning a Bluetooth enabled mobile phone can easily access reliable transmission for both voice and data. Untethered a Bluetooth hotspot to browse the Internet without having to Bluetooth devices will eliminate the need for cables and carry a PDA or a laptop. provide a bridge to existing networks. Two devices must have the same type of link in order to Today, the majority of people are in possession of a mobile establish communication. The concept behind a Bluetooth phone. The number of mobile phone users is increasing each communication is the use of “masters” and “slaves”. The year. Mobile phone creates more possibilities for social master device works as the moderator in the communication networking. The deployment of Bluetooth hotspots will between itself and the slave devices as well as between the widen access to broadband services using mobile phones not slave devices themselves. Bluetooth hotspot uses this master only to professionals and mobile workers but more importantly, to other segments of consumers who want to go slave architecture were Bluetooth server acts as the master on-line for non-business related and sociable purposes, and and other Bluetooth enabled mobile devices as slaves. to consumers who do not own PCs.

III. BASIC STEPS

Steps to be followed in Bluetooth hotspot are: • Connectivity • Authentication and security • Data transfer

In Bluetooth hotspot we require a Bluetooth server with Fig. 1. Piconet master slave Bluetooth architecture internet connection in it, Any Bluetooth enabled mobile

Copyright to IJARCCE www.ijarcce.com 4894 ISSN (Online) : 2278-1021 ISSN (Print) : 2319-5940 International Journal of Advanced Research in Computer and Communication Engineering Vol. 3, Issue 1, January 2014 which wants to be connected to Bluetooth server and use the B. Communication link method: services provided by it. A communication link is data transmission connection between a master and slave for sending and receiving data The process starts with connectivity process in which packets. Bluetooth server sending a message of pairing to all the discoverable mobile devices in its range. As the services of The master sets up a communication link to a slave by using Bluetooth hotspot are to be provided to authorized users slave information when the master establishes a connection various security issues like eavesdropping and false with the slave, and it controls data transmission to confirm authentication are considered. The devices receiving the whether the slave can communicate with it[5]. message need to send an appropriate response (passkey) to the server back to complete the authentication. Now the connection link is established and the data/ file transfer can take place. Now the server sends the client program which needs to be installed on the mobile devices. After installation client requests for the web page which is queued at the server site and maintained by hotspot manager which keeps tracks of what request is made and who requests it. Now the request is taken out from queue one by one and requested page is fetched from internet. This page is now converted into mobile format by the HTML parser and Fig. 3. Communication link Method sent to the appropriate client who requested it. Due to some erroneous detection in the above methods they Now we will see in detail the connectivity, security and data were improved and were renamed as: transfer mechanisms in Bluetooth.  Advanced inquiry method, IV. CONNECTIVITY  RSSI method. Identification and authorization are the two important steps for having trusted connection between two Bluetooth devices. Connectivity is the first step for establishing any A. Advanced inquiry method: connection[5].This can be achieved by using two methods If the Bluetooth function of the PC (master) gets the slave namely, information of the authentication key once within a set period of time, the advanced inquiry method judges that the • Inquiry method (Inquiry function of Bluetooth) user is sitting in front of the PC[5]. • Communication link method (Monitoring B. RSSI method: communication link) RSSI (Received Signal Strength Indication): In A. Inquiry method: telecommunications, RSSI is a measure of the power of a The inquiry method detects the user's presence by using the received radio signal; that is, RSSI quantifies the strength of inquiry function. The Bluetooth device of the PC (master) a radio signal. In general, the value of RSSI decreases as the gets the slave information of surrounding Bluetooth devices relative distance with a communication partner increases. by running the inquiry function regularly. The PC then RSSI can therefore be used as a measure for expressing judges that the user is sitting in front of the PC if the relative distance with a communication partner[5]. acquired slave information indicates that the user’s In this method the PC begins to compare the RSSI value and Bluetooth device is specified as an authentication key[5]. the threshold value that was set for user. The PC judges that the user is sitting in front of the PC if the RSSI value is higher than the threshold value The communication link method can be finely controlled by comparing the RSSI and threshold values. To develop a presence-detection system with high detection accuracy at modest cost, a presence-detection method using the received signal strength indication (RSSI) function of a Bluetooth device was developed. The performance of this method under various environmental conditions was evaluated by a simulator[5].

Fig. 2. Inquiry Method

Copyright to IJARCCE www.ijarcce.com 4895 ISSN (Online) : 2278-1021 ISSN (Print) : 2319-5940 International Journal of Advanced Research in Computer and Communication Engineering Vol. 3, Issue 1, January 2014

Consequently they are able to eavesdrop on any traffic based on this key[1]. Authentication is performed with a challenge response scheme utilizing the E1 algorithm. E1 is a modification of the block cipher SAFER+. The scheme operates as follows: The verifier issues a 128 bit long challenge. The claimant then applies E1 using the challenge, its 48-bit Bluetooth address, and the current link key. He then returns the 32 most significant bits of the128 bit result. The verifier confirms the response, in which case the authentication has succeeded. In this case, the roles are switched and the same Fig. 4. RSSI Method procedure is applied again, there by accomplishing mutual authentication[1]. V. SECURITY The Bluetooth challenge response algorithm differs from that used in 802.11b in very important ways. In 802.11b the When a user sends data over a wireless network, he has a challenge and response form a plaintext/cipher text pair. reasonable expectation that such data is not easily readable This fact, combined with the simplicity of the encryption by unauthorized persons. Unlike a wired network, which method (XOR), allow an intruder to easily determine the requires a physical intrusion, wireless data packets can be authentication key string by listening to one authentication received by anyone nearby with an appropriate receiver, procedure. In contrast, the Bluetooth authentication method potentially outside the physical security barriers of an never transmits the complete challenge response pair. In organization. addition, the E1 algorithm is not easily invertible. Thus even There are basically two main security issues in wireless if an attacker has recorded an authentication challenge technology which are needed to be considered for trust response session, he cannot (directly) use this data to building between two devices. compute the authentication key[1]. The known attacks on the E0 cipher used in Bluetooth are  Eavesdropping far more computationally complex then corresponding Eavesdropping is the act of secretly listening to the private attacks on RC4 used in 802.11b. As yet, no practical direct conversation of others without their consent. attack has been reported[1].  False authentication The known attacks on 802.11b security have been discussed and found not to apply to Bluetooth wireless technology. In The present system WI-FI hotspot has both these security particular issues. Now let us see how these issues are handled in Bluetooth technology. i) 802.11b authentication is highly susceptible to impersonation by recording only one authentication Bluetooth technology provides a method for authenticating procedure. This is facilitated because a plaintext/cipher text devices. Device authentication is provided using a shared pair is transmitted. Bluetooth communications do not share secret between the two devices. The common shared secret this limitation. is called a link key. This link key is established in a special communications session called pairing. All paired devices ii) 802.11b encryption is not very secure. The RC4 share a common link key. There are two types of link keys: implementation used in 802.11b has several well-known unit keys and combination keys[1]. direct attacks. Currently known direct attacks on the Bluetooth encryption are computationally complex and of A device using a unit key uses the same secret for all of its little practical value. connections. Unit keys are appropriate for devices with limited memory or a limited user interface. During the VI. DATA TRANSFER pairing procedure the unit key is transferred (encrypted) to the other unit. Note that only one of the two paired units is Data is transferred using packets. To transfer data, a link allowed to use a unit key. needs to be established between the devices. i.e establishing Combination keys are link keys that are unique to a a packet transport mechanism. One can start adding higher- particular pair of devices. The combination key is only used level protocols such as the familiar Internet protocols IP, to protect the communication between these two devices. TCP, UDP and, on top of that, to name a few, HTTP and Clearly a device that uses a unit key is not as secure as a FTP. This eventually leads us back to the automatic file device that uses a combination key. Since the unit key is transfer implied by the scenario[4]. common to all devices with which the device has been Between two (or more) Bluetooth devices two types of links paired, all such devices have knowledge of the unit key. can be established, namely:

Copyright to IJARCCE www.ijarcce.com 4896 ISSN (Online) : 2278-1021 ISSN (Print) : 2319-5940 International Journal of Advanced Research in Computer and Communication Engineering Vol. 3, Issue 1, January 2014

• Synchronous Connection-Oriented (SCO) link 2745 bit packets possible? The answer is that a packet may span up to five time slots, during which the channel The SCO link is typically used for time-bounded data, such frequency is kept constant[4]. as voice. An SCO link is implemented by reserving time slots at a regular interval for data exchange. B. Packet Types • Asynchronous Connectionless Link (ACL) Bluetooth supports a wide variety of packet type depending The ACL link works as a traditional packet switched on the type of link, throughput and bit fault tolerance. On network. Packets are transmitted only when necessary. SCO links packets for low, medium and high quality voice as well as combined data and voice are supported. For ACL A. Bluetooth Packet Format links 1, 3 and 5 slot packets using medium (5 check bits for each 10 bits) and high (no additional check bits) data rates The standard Bluetooth packet consists of three parts: the are supported[4]. access code, the header and the payload C. Media Access

With the term “media access” one understands the means and procedures used by a device to gain access to the

Fig.5 . Bluetooth packet format transmission medium. On a Bluetooth channel media access is handled by dividing the time slots into two groups: i) The Access Code: master-to-slave and slave-to-master slots. The master can only initiate transfer in even-numbered slots The 72-bit access code is mainly used to identify packets (the slots being numbered by the Bluetooth channel clock) transmitted over a Bluetooth channel. All data packets sent and replies from the slave can only be transmitted in odd on the channel share the same access code. In addition, the numbered slots. A slave may only transmit in the slave-to- access code is used for device paging (finding out if a master slot if it was addressed in the previous master-to- specific device is in range) and inquiries (used to discover slave slot. It is up to the master to reserve enough slave-to- new devices). A Bluetooth device monitors the access code master channel capacity[4]. of each packet; if the device is not directly or indirectly addressed, the rest of the packet is ignored .The access code is very fault-tolerant, so up to 6 bit errors can be corrected. The access code is also used to determine receiver timing[4]. ii)The Packet Header

The 18-bit packet header contains the following Information:  A 3-bit target device address, which addresses an active device on the Bluetooth channel. A broadcast address is also provided.

 A 4-bit type code. Identifies the type of data or control packet. Fig. 6. Master/Slave transmits and receives timings  Fields for flow control, sequencing and packet acknowledgement. D. Packet Acknowledgement and Flow Control  An 8-bit header CRC. To protect the header from transmission errors each bit is repeated three times in row When transmitting data or data/voice packets an (the Bluetooth spec refers to this as 1/3 FEC encoding) unnumbered ARQ (Automatic Repeat Request) scheme is yielding a total length of 54 bits[4]. used. Such packets are retransmitted until an acknowledgement of successful reception is received, or a iii)The Packet Payload: timeout occurs. The acknowledgement (either positive or negative) is piggy-backed onto the header of the return The payload part (0 to 2745 bits) of the packet carries the packet. A missing acknowledgement (e.g. the return packet actual data. For ACL links, the payload begins with an 8-or was lost) is treated as a negative acknowledgement. In case 16-bit header, which indicates the length of the data packet of master-to-slave transmission, the return packet is sent in and provides fields for logical channels and flow control. the subsequent time slot. When the slave transmits the return The header also supports fragmentation of data packets. The packet is received the next time the master addresses the careful reader notices that during the Bluetooth time slot of slave[4]. 6.25mS you can send a maximum of 625 bits; how are then

Copyright to IJARCCE www.ijarcce.com 4897 ISSN (Online) : 2278-1021 ISSN (Print) : 2319-5940 International Journal of Advanced Research in Computer and Communication Engineering Vol. 3, Issue 1, January 2014

In order to distinguish the cases when a packet was successfully received, but the acknowledgement was lost and successful acknowledgement, a 1-bit sequencing number is used. If a packet it resent, the sequence number is held; this way the recipient will detect duplicate packets. If the receive buffer fills up, a Bluetooth device may stop the transmission by resetting the FLOW field in the return packet. This “stop” signal does not affect control packets. If the return packet is not received, a “go” signal is assumed[4]. REFERENCES

[1] Thomas G. Xydis Ph.D, Simon Blake-Wilson. “Security Comparison: Bluetooth™ Communications vs. 802.11”. Bluetooth Security Experts Group. 11-10-2001 revised 2-1-2002 [2] Bluetooth Special Interest Group. https://www.bluetooth.org/About/bluetooth_sig.htm [3] Nateq Be-Nazir Ibn Minar and Mohammed Tarique. “A Secured Bluetooth Based Social Network” published in International Journal of Computer Applications (0975 – 8887) Volume 26– No.1, July 2011. [4] Tancred Lindholm. “Setting up a Bluetooth Packet Transport Link” Department of Computer Science,Helsinki University of Technology. [5] Masataka Kikawa, Takashi Yoshikawa, Shinzo Ohkubo, Atsushi Takeshita, Yoh Shiraishi, and Osamu Takahashi. “A Presence-detection Method using RSSI of a Bluetooth Device”. International Journal of Informatics Society, VOL. 2, NO. 1 (2010) 23-31.

Copyright to IJARCCE www.ijarcce.com 4898